


A Mutually Beneficial Arrangement

by DemonMamoru



Series: A Prisoner with Benefits [1]
Category: Undertale (Video Game)
Genre: Aftercare, Bondage, DUB-CON DUB-CON MY KINGDOM FOR ALL THE DUBCON, DUB-FUCKING-CON, Dark, F/M, Fluids, Implied Masochism, No Fluff, No Romance, Not cute, PWP, Skeleton Sex, Smut, Smutty, Undertail, Unusual Sex, Voice Kink, biting kink, bone zone, catch-22 situation, cum inflation kink, distance orgasm, dub-con, high levels of fucked up all up in this bitch, liquids, magic applied to sex, magic based sex, magic kink, not a good situation for the reader, of-age reader, orgasm denial (implied), orgasms control, plot is only for background info, reader is 18+, reader is fully capable of sexual consent, reader/UF!Sans, said it again for the people in the back, stretch kink, sub/dom
Language: English
Status: Completed
Published: 2016-02-09
Updated: 2016-02-09
Packaged: 2018-05-19 07:10:44
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,460
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5958343
Author URL: https://archiveofourown.org/users/DemonMamoru/pseuds/DemonMamoru
Summary: <blockquote class="userstuff">
              <p>"You know, if that wasn't getting you off, you could have just said so."</p>
            </blockquote>





	A Mutually Beneficial Arrangement

**Author's Note:**

> Dub-con (Reader is getting protection from Sans in exchange for the type of content that you are here for. Using dub-con because the reader does not have much of an actual choice, it's either staying with Sans and live and be taken care of, and it's not like Sans couldn't take them by force but he gave them a catch-22 of a choice, or chance the rest of the Underground full of monsters just dying for a chance to get the seventh human soul that can release them from the mountain. The reader themselves also understands that these monsters-since this is an AU-are more than ready to pay back humankind for their time spent sealed away, and would be a serious threat to humans. They know their significance as explained by this AU's Flowey/Asriel and know that they can be used by Asgore to unleash a war. However, with the threat that Toriel and the Froggits represented, Flowey recommended to move on, as Toriel would have killed all the humans that had come down if they had not, as he witnessed their deaths and their Saves/Reloads. This content is purely smut and meant to be a oneshot, although I have thought up a situation and background for this AU. If you would like to know more about it, message me on tumblr. And reader is not Frisk. And as this kind of content is intentionally sought out by the fandom, I make no apologies for anything here and I doubt I'll get flames. I also emphasize that Sans understands that human bodies, while stronger than monsters, need good conditions to be able to be healthy. Sans isn't doing aftercare and making sure the reader has food and water and necessities because he cares for them, it's because he understands that toys that last are ones that are taken care of. Like how a car lasts by the care taken to keep up with maintenance, the same idea goes here. Sans knows the human reader will be amenable towards him if he keeps them healthy and happy and with their own space. He isn't caring, he is just doing what's necessary to keep the reader content so that he can keep them and so that they won't fight against him so bad.) And I've finally sunk to the depths of the other skele-sinners on this site, so I'll leave this as my final note for this fic: 
> 
> I know I'm going to hell for this, but you're here reading this by your own choice and free will, so see you in Hell mother fuckers.

The shed was surprisingly well built, which made you wonder as to whether or not Sans (who seemed like he didn't do things or really put effort into doing them well) had anything to do with it's construction or plans. But at least it was warm compared to the outside. The heater in the corner hummed merrily, making ambient noise.  
  


The floor was smooth black tile for the most part, except in the corner where a bed was, which had a scarlet rug underneath it. The bed had black sheets and blankets, a couple of pillows. There was window that faced towards the forest, the trees could just only be made out in the dim light of the Underground.

 

The walls were plain, painted red, but no decorations or paintings or pictures hung on them. There was a small bathroom that had been added on and the door to it was open. It was cramped with a small sink, a toilet, and a bathtub/shower combo. There was a sofa that was sitting opposite a small entertainment system. A small fridge and freezer were under a cubbard, on top of it was a microwave. The shed was effectively a one-room apartment with all the needed amenities to live day-to-day.

 

The only thing was that you couldn't leave. The shed was lockable from the outside and the inside. You could access the inside locks, but the outside lock was magic-based, and could only be opened by either Sans, or his brother, Papyrus. And Papyrus never came in the shed. He claimed he wanted nothing to do with anything in it, since 'SANS, THE INSIDE OF YOUR 'SHED' MUST BE SIMILAR TO THAT MESS YOU CALL YOUR ROOM. I REFUSE TO SET FOOT INSIDE IT ON PRINCIPEL.' that's what you had heard Papyrus says to Sans after Sans invited him to come inside. Sans shrugged him off, and came in with a few frozen meals that he threw in the freezer for you. You were pretty sure that Sans had asked Papyrus that just to make sure that Papyrus would avoid the shed entirely. In fact, you would debate the title of 'shed' for this place, as it would actually be considered a nice one-room apartment on the surface.

 

Your 'safety' of being kept in this shed was on a few conditions, and at the top of that list was 'do what Sans wanted'. Truth be told, he seemed actually nicer than most monsters, but he more than made up for that by being a manipulative little bastard. He was sadistic, cunning, and malicious. He didn't kill you because he said you were worth more alive. Which you took to mean that he wanted you for his own personal reasons, or he wanted you to be alive so he could hand over your soul to the king at any time of his choosing.

 

But you guessed it was personal reasons.

 

Those personal reasons were that Sans was seven different kinds of fucked up-in the literal sense.

 

Your hands were cuffed above your head, crossed over at the wrists. You were sat on a chair that was pretty beat up and made of cheap plastic. There was no back rest, and the chair had a few holes in the seat, but it held your weight. Your shirt was still on, although your bra had been taken off by the skeleton that was keeping you. Your jeans, however, were not, neither were your underwear. At least, you thought again, that it was warm inside. At least warm enough to the point that you weren't in complete discomfort from the temperature alone.

 

The tendrils of scarlet red magic that pulsed and wriggled inside of you was the proof. They thrummed with magic, sending tingling sensations throughout your core. Since they were magic, they were a part of a living being and they were constantly moving. Every so often, they stilled, shuddered hard, and a hot fluid would gush into you. Then movement would resume, and the liquid released would be massaged into your walls, reslicking you and allowing for easier penetration. You had been like this for probably a couple of hours, you had lost track of time anyhow. The situation aside, you couldn't say that you were in that much pain right then.

 

The stretch wasn't so intense that it was uncomfortable, and if you could over look the situation that you were in, you could even admit that this felt kind of good. No toy you ever had had been able to move like what was in you right now. A mixture of your arousal and the released fluid (you guessed it was to help keep you lubricated) seeped out of you, smearing your inner thighs and dripping out onto the floor, a puddle had formed quite some time ago.  
  


But, despite what you had gone through, there wasn't enough stimulation to tip you over the edge, although you were certainly pleasured enough to keep you turned on as the time passed. You were, however, frustrated. You would like to come and then be able to sleep, thank you very much.  
  


The skeleton that had put you in this situation was sitting on the couch, headphones on, reading a book that had a title that you couldn't make out from where you were. Deciding to take matters into your own hands, you brought a leg up onto your chair, knee pointing out, heel of your foot pointing towards your entrance, and pressed and ground it against what was in you, forcing it just a bit deeper, stretching yourself farther back inside, hitting a nerve cluster that hadn't been in contact before. The tendrils of magic seemed to react to what you did, this time pressing forward and rubbing against that spot as if they got the message and knew what to do with this new information.

 

Then, the pulses started strong and slow, a thickening of what was in you starting from the base of them to the end, building like a wave as ground down harder, using your foot to push the magical apendages in and rolling your hips in counter point. You bit down on your lip to try and hide your moans, but it only partially worked.  
  


“Girlie,” a bass voice said.  
  


You opened your eyes, having closed them to try and forget your situation and just enjoy the sensations, and watched as Sans put his book down and pulled the headphones off. He stood off the couch. He looked much thinner without his puffy black jacket on, with only a loose fitting red t-shirt.

 

“That magic that I put in you is a part of me, I can tell what you're doing to it, to me,” he drawled as he came closer. He stood over you, not being especially tall but you were sitting down. His cold phalanges of his fingers grazed over your cheeks as the red iris in his right eye socket glowed.  
  


You inhaled sharply as the magic inside you widened and lengthened.  
  
“And if I wasn't getting you off,” he chuckled, his voice was rumbling and deep and listening to it felt like sex for your ears, making your flush as your body overrode your pride and a mixture of a sigh and mewl escaped your lips, “you could have just said something.”

 

The magic was pulled out of your, thrust back in slowly, letting you savor the sensation of being filled just right, before being pulled out again, the tempo slightly increasing.  
  


“Or maybe you just don't know what does get you off? Human anatomy is weird, and even your kind don't understand it, if the human propaganda that we find down here is right,” Sans chuckled again, trailing his fingers down your throat to your shoulder, then diagonally across your breast and down your stomach. His hand settled on your pelvic bone, thumb rubbing circles.  
  


Your pulse jumped whenever Sans spoke, pulse quickening in the hopes that you'd finally be able to get off, after being pent up for so long.  
  


Sans red eye was focused on your neck, and he saw the tell-tale jump of your jugular in your neck as he spoke again, checking to see if it was just timing.  
  


“Aside from that...you don't have to keep things from me,” his hand moved down to your clit, a cold finger tip encircling it, your breath hitching, “this thing between us will be...mutually beneficial,” he leaned forwards as his other hand came to the side of her neck to feel for your heart-beat, “if you just tell me how you want it,” he purred. Ah, there it was. A jump, a twitch in the jugular and a matching squeeze of your wet, hot walls on his members inside you. He ground down a groan of his own, needing to keep the appearance of control.  
  


Sans knew he had got you now.  
  


“If you're shy now, that's ok. You can tell me _anything_ ,” his voice rumbled in your ears. “If you don't want to, that just makes it fun to figure out. And I have some idea of how you work, but poor you-you don't know much about monsters, do you?”  
  


You shook your head as the speed of what was moving in and out of you increased and the moving magic actively sought out more of your nerves to grind against.  
  


“It's only fair I tell you, I s'pose. For example,” he pulled back into your range of vision, his skull a few inches from your face, “you probably didn't know that I've been getting off this whole time, did you?”

 

Your eyes widened in surprise.  
  


“Yeah, that rush of liquid? It was me having a good time. That doesn't have to happen, but I read someone that's how it happens to human guys. And as it turns out, it's good to keep you wet and slick. And you're so soft,” he groaned out. “Goddamn, you're so _soft_. It feels like heaven,” he sighed happily. You almost didn't catch it as you became numb to your surroundings. All that mattered was the length sinking into you, the thumb around your bud, and that fucking _voice._

 

If your face could have gone redder, it seemed it did, judging by his toothy smirk at you.

 

“Oh, and it's so nice to watch my come drip out of you, feel you just continue to be soaking wet for me,” his breath blew gently across your face. His thumb toyed with your clit, faster circles making your spine tingle and legs shake, as he increased his pace. Sweat started to form on his skull, slicking down the sides and dripping from his cheekbones. “Hell, it feels so good to just feel it slip out of you,” he hissed.  
  


You were almost gone now, just a little bit further...!  
  


He pulled down one side of your shirt, nuzzling the skin at the base of your neck and meeting of your shoulder. 

  
“Come for me,” he rumbled as the magic inside of your seemed to go into a frenzy. The combination of that feeling, with how expertly he played with your clit and that deep voice in your ears finally tipped you over the edge, your inner muscles clenching down tightly, gripping the magic in you and seizing down as if to draw him in further and never let go sent Sans along for the ride. Your lips parted as you gave a yelp. His teeth sank into your flesh, causing some pain that your mind was more than willing to not pay attention to right that second. You repaid him anyway, biting down on his clavicle to muffle yourself.  
  


A couple more pushes into you, and he came as well, filling you with a much longer outburst of fluid from his member than the other times before. As your both came down, you paid more attention to the bite on your shoulder. It stung, providing a mentally clearing sensation as the sharp stings pulled your mind back to reality. Your jaw unclinched from his clavicle, drool having seeped out over the white surface. Sans face reentered your sight, and he smirked in approval at you. The member within you wasn't there, but neither was his ejaculate spilling out. You wanted to ask, but you also were sure that you might not be able to deal with the answer. Whatever was keeping the hot liquid in wasn't stretching you and there wasn't any discomfort, actually it seemed to have the opposite effect, making you feel content and warm with the added weight. There was something oddly satisfying about it, if you were being honest with yourself.  
  


“Well, I'd say that was good for both of us,” Sans chuckled again as you gave slight nod. With a snap of his fingers the cuffs opened and your arms were able to flop down. He went off the to the bathroom and you heard the sound of water running. You did want to shower, but you honestly doubted your legs capability to hold you up at the moment, so you waited for Sans to come back. When he did, he was holding a wet wash clothe. He picked you up off the chair, and had you brace your hands and support your weight on his shoulders as he wiped you clean of your activities. Once he was done, he wiped his own fingers and tossed it over by the chair. “I'll clean up later,” he said as he picked you up and took you over to the bed. He pulled the sheets back and put you down.  
  


You turned back over to take a look at him and get comfortable, and when you seemed to settle he pulled the blankets back over you.  
  


“See, that wasn't so bad. You keep up performing for me like that, and you won't have to worry. You'll be well taken care of, and kept safe. There anything you need?” he stroked your forehead in a fond manner.  
  


“Water,” you said. He left and brought over a bottle of water that he pulled from the fridge and opened it for you. You took a few swigs and handed it back. He set it on the small nightstand so it was within reach.  
  


“Anything else?” You shook your head and closed your eyes, and let yourself go to sleep, dragged there by physical and mental exhaustion. Your mind was still in a state of chaos, but your body was too tired to care, and you desperately needed time to come to terms with your new situation. Things would feel better in the morning you said to yourself as you drifted off into welcoming darkness.  
  


 

**Author's Note:**

> The spacing is weird for some reason, and I don't know how to fix it.


End file.
